Kielder Reservoir, the largest in Britain, has also been subject to the largest expenditure on objectives other than water supply. The northern arm of the reservoir was impounded by an 'amenity dam' at Bakethin which cost ,1.65m. It protects this part of the reservoir from variations in water level and enhances its value as a nature reserve (Rocke 1980). But it is ugly [Fig 5.12].